FastFire BRONZclay Success!

After feeling a bit "burned" by base metal clays a few months ago, I went ahead and tried a new brand on the recommendation of jewelry artist Evelyn Pelati.  I went with FastFire BRONZclay by Metal Adventure and was happy with the results for a variety of reasons.  Here are a few...

To begin with the obvious, it fires fast.  It takes an hour to ramp and an hour to fire.  It is a one phase fire, so set the kiln and forget it.  I was looking for a base metal clay to use with multiple classes, so I do not always have the luxury of being able to run a multi-phase firing during my teaching schedule.  This allows me to not have to return to run a firing on my own time. 

There is the other obvious of the price, with bronze clays being around 30 cents a gram and silver clays being more than $2 a gram, it is the most economical, especially for introducing it to a large class.

The firing directions are clear and easy, particularly if this is your first attempt at base metal clays.  The descriptions of what you will find out of the kiln and what that means for your firing temperatures are also clear.  I was able to figure out my firing schedule after just two test fires, though I have had to make adjustments based on running a whole class worth of pieces at a time.

I have also been able to successfully fire in a ceramic firing vessel.  Since I am flip-flopping between silver and bronze, depending on the class, I am running multiple firings a day.  When you fire in a steel pan there is a black flake sort of fire scale that needs to be vacuumed from the kiln after your firings.  With a ceramic vessel, there is no evidence of the base metal firing.

Last, the workability of the clay has been great.  It has a silky flexibility that makes it great for draping and forgiving for students just learning to work with it.  When it dries, it is easy to reconstitute and continue working.

These were a couple of quick test pieces where the clay was rolled into scratch foam designs and run through the firing.  The bronze has a warm gold hue and nice weight once fully sintered.  

White Bronze Continued

 For those of you keeping track, this is my fourth test fire with White Bronze.  Those first three trials can be seen in last week's post.  After contacting the manufacturer, I took their specific notes on my previous firing trials and began by elevating the firing vessel even higher.  I increased it's height by adding another set of stilts so that its rim sat just below the top of the kiln.  This was recommended since even in my small counter top kiln the difference in temperature from floor to lid can be 300 degrees.  My next step was to do both phases of the firing with the pieces buried in the coconut carbon, it was stressed that White Bronze MUST be buried even for the binder burn off phase with the lid off the vessel.  Since both phases are being done buried in the carbon in the kiln, there was no need to cool in between, so I took the recommendation of the following schedule:

RA1: Full 

PF1:1000F 

HOLD:2hrs

RA2: Full 

PF2: 1250F 

HOLD:2hrs

RA3: 000

START

The above image on the left shows the char on top of the carbon after the completed firing had cooled.  This time I definitely smelled more of a "campfire" smell from the kiln than the previous firings, so I do believe it got significantly hotter.   On the right you can see the test pieces out of the kiln, they already appeared stronger.  There were no cracks and they handled well, so I had hope that the firing had been successful.  I took some 220grit sandpaper to the test pieces and removed enough fire scale to reveal a metallic interior.  As I had found out last week, the water drop test does not apply to White Bronze and the way to check is to sand with 220 grit to reveal the bronze, without small particles coming off.  I was really excited and gave the pieces a wiggle with my fingers, at which point they each snapped in the middle.  

Grrrrrrrrrr!  

So back to the drawing board.  What I do know is that the carbon burned hotter this time and the binder appeared to successfully burn out.  What I don't know is whether the White Bronze was at its full firing strength.  The other thing I learned last week was that even when fired properly, it is very fragile and should really never be used alone.  It was recommended that it be used in combination with other materials for strength.  If it is used alone and fired successfully, customers need to be warned that it is a very fragile material and does not have the traditional strength expected from metals meaning the introduction of other tools such as hammers or pliers would result in it breaking, as well as if it is dropped on a hard surface.  My question still remains as to whether or not I should be able to break it with my fingers.  I plan to email these results to the manufacturer to see if this really is the brittle level of this material or if I should slowly bump the second phase firing by 10 degrees.   I will keep you posted...

White Bronze Explorations

I've spent the last few weeks exploring White Bronze Metal Clay.  The clay comes in powder form and can be mixed easily.  The mixed clay is silky and flexible.  It was easy to work with and was quick to sand.   I was excited to see how the pieces came out once fired, but that's where my trouble began.  So far I have fired three different test pieces, each ending with different problems.  Below is a page from one of my firing notebooks, and at the bottom are the results.  Test Fire #1 was based on the directions from the clay, in the end the center appeared sintered, but the edges were fragile enough to snap off.   Base metal clays must be fired buried in carbon, this is done inside a vessel in the kiln.  For test firing #2 I altered my firing parameters based on suggestions from my vessel's manufacturer.  This time, the piece was far weaker and crumbled like a cookie when wiggled.  For my third test fire, I reached out to other metal clay artists working in bronze and adjusted my firing schedule accordingly.  This resulted in the piece splitting and then crumbling.  

I was reassured by other metal clay artists that initial explorations in bronze required several test fires since everything from the kiln type to carbon type to vessel type to bronze type effects firing, but was still a bit disheartened.  I contacted the manufacturer of the white bronze and they immediately responded.  You can see in my firing notes below their direct feedback on my trials.  The key points include the following:

-The water drop test used in other bronze clays to check for sintering, is not a valid test for White Bronze.

-Both phases of firing must be done in a kiln, buried in carbon - this includes the first phase where the binder is burned off.

-Even the small kiln I use for firing can have a 300 degree difference from the floor to the lid, so the vessel must be up on stilts to best achieve high temperatures.

-The lid should be off the vessel for both phases of the firing.

-When both phases of firing are done in the kiln, there is no need to cool in between.

-The following firing was recommended:

Vessel on Stilts/No Lid for entire firing

Piece buried for entire firing

Phase 1:  Full Ramp to 1000F hold 2hrs

No Cool

Phase 2:  Full Ramp to 1250F hold 2hrs

Test cooled pieces with 220grit sandpaper, if it is metallic it's good.

*** On a side note, the instruction manual for White Bronze is part of the manual for the entire collection of base metal clays and therefore a little confusing as they are all talked about together.  In the manual, it does say it is a brittle metal when made into thin pieces and recommends it being used in combination with other clays for strength.  The email response I receive basically asked why I would be using it alone to begin with and that it NEEDS to be used in combination with other metals.  That it should not be used alone and even if you do get it to fire correctly, customers need to understand that their piece will be VERY fragile.  This really is different than how it is presented in the manual.  I went back and checked on the manufacturer's website and no where does it note that White Bronze is any different than the other base metal clays, you only learn that once you download the manual which I imagine most people do not do until they order it.  This is something which I find a bit frustrating, it should be more clearly noted as part of the product description.  I really didn't see the red flags until the manufacturer questioned my use of it because the manual is not that direct.  My persistence in firing it correctly is partially to see the process through and partially to complete the handful of pieces I have in White Bronze that are waiting to be fired.

So my next step?  More test pieces next week based on the above suggestions.  Wish me luck!